Authors:V. Balek, V. Zeleňák, T. Mitsuhashi, S. Bakardjieva, J. Šubrt, and H. Haneda
Results of emanation thermal analysis (ETA) characterizing microstructure changes of SiC based materials during heat treatment in argon are demonstrated. This method made it possible to reveal fine changes of the texture of SiC nano-sized powders, SiC micro-sized powders and SiC whiskers under in situconditions of the heating. ETA curves can serve as fingerprints of the respective samples.
Emanation Thermal Analysis (ETA), based on the measurement of the release of radon from previously labelled samples, has been
used for 'in-situ’ characterisation of the morphology changes of intercalated montmorillonitic clay. The thermal behaviour
of hydroxyaluminium intercalated montmorillonite was monitored in course of the preparation of alumina pillared montmorillonite,
making possible to determine optimal temperature for the isothermal treatment of the intermediate product. Moreover, the thermal
stability of alumina pillared montmorillonite porous structure was determined from the ETA data. A good agreement of ETA data
and surface area, XRD patterns. DTA, and TG resulted was found.
The background for the modelling of radon diffusion release from disordered solids is given and used for the simulation of
emanation thermal analysis results characterizing the annealing of structural irregularities that serve as radon diffusion
paths in the solids.
Authors:V. Balek, J. Šubrt, T. Mitsuhashi, I. Beckman, and K. Györyová
The paper reviews the actual state of the development and use of emanation thermal analysis (ETA). Examples of its recent applications are presented. The advantages of ETA in the microstructure characterization of materials under in situ conditions of their heat treatment are outlined.
Authors:T. Sato, M. Hubáček, V. Balek, J. Šubrt, O. Kriz, and T. Mitsuhashi
Processes taking place during formation of B-C-N ceramics by thermal treatment of organic precursors were investigated using
emanation thermal analysis (ETA), differential thermal analysis (DTA) and thermogravimetry (TG). An additional information
about thermal behavior of precursors used for preparation of BC4N, BN and CNx ceramic systems by heating in argon up to 1100C
was obtained. The ETA enabled us to characterize microstructure changes in the samples at in situ conditions of thermal treatment.
A good agreement of ETA, TG and DTA results was found.
Authors:V. Balek, Z. Málek, J. Šubrt, M. Guglielmi, P. Innozenzi, V. Rigato, and G. Della Mea
Emanation Thermal Analysis (ETA) was demonstrated as a tool for the characterization of microstructure changes of a sol-gel
precursor for silica-titania layers deposited on the glass plate to be used as planar waveguides. Temperature ranges of 280-330
and 380-500C, respectively, in which the densification of the layers took place, were determined by ETA under in situ conditions
of the sample heating. Results of thermogravimetry were compared with the ETA data.
Authors:V. Balek, T. Mitsuhashi, I. Bountseva, I. Beckman, Z. Málek, and J. Šubrt
Emanation thermal analysis (ETA), based on the measurement of the release of radon previously incorporated into the sample, was used to characterize the differences in the thermal behavior porous titania film (thickness 200 nm),when heated in argon and in oxygen, respectively, in the range from 20 to 800°C. It was observed that the annealing of porosity and structure defects in the near surface layers of the porous titania film (anatase) was enhanced on heating in oxygen in comparison to the heating in argon. ETA results were compared with SEM micrographs and XRD patterns of the titania film samples heated to 500 and 800°C, respectively. A mathematical model was used for the evaluation of the temperature dependence of the titania films microstructure development.
The theoretical background for the use of radon diffusion as a probe of microstructure changes in solids is given. The high sensitivity of the emanation thermal analysis (ETA) in the study of solid state processes especially interactions taking place on surfaces and in the near surface layers is described. The increasing sensitivity of the method towards bulk processes with rising temperature is theoretically shown. The background considerations to be used in the mathematical modeling of temperature dependences of the radon release from solids on heating (i.e. simulated ETA curves) are presented. Various models for radon diffusion and various functions describing the annealing of structure irregularities, which served as diffusion paths for radon, were used in the modeling. It was shown, that ETA is able to characterize microstructure changes in the surface layers of the thickness from several nanometers to several micrometers.
Authors:V. Balek, V. Zeleňák, T. Mitsuhashi, I. Beckman, H. Haneda, and P. Bezdička
Emanation thermal analysis (ETA) was used in the characterization of microstructure changes during heating ofprecursors for the titania based materials: hydrous titania, TiO2nH2O (n=0.58) and hydrous titania containing 10% ruthenia,(TiO2)0.9(RuO2)0.1nH2O (n=1.5). The precursors were heated at the constant rate 6 K min–1 in argon flow in the range 20–1000°C. ETA results were compared with the theoretical curves simulating the temperature dependences of radon release rate, E(T). Two mathematical models were used in the simulation. The models considered either subsequent or simultaneous solid state processes (i.e. dehydration, crystallization orphase transition, resp.) during thermal treatment of titania based materials. A good agreement was found between experimental and the simulated ETA curves. The results of ETA were confirmed by XRD patterns of intermediate products of thermal treatment of the precursors.
Computer modelling of time dependences of radon release rate during hydration of 3CaO·SiO2 was carried out. It was demonstrated that the emanation thermal analysis (ETA) can be used for the characterisation of morphology changes during hydration of Portland cement clinker minerals. The presence of various additives and increased temperature affecting kinetics of hydration were simulated by the mathematical model of the radon release rate during hydration of 3CaO·SiO2. A good agreement between the mathematical model and ETA experimental results was found.